1. Field of the invention
This invention relates to an ink jet head which performs recording by jetting a liquid to form flying droplets, an ink jet cartridge by use of said head and an ink jet recording head by use of said cartridge.
2. Related background art
Ink jet heads utilizing the method of generating heat energy by use of an electrothermal transducer and imparting the energy to ink, thereby causing abrupt change in the state accompanied with formation of bubbles of ink to discharge ink through discharge droplets and form flying droplets, can be easily made compact in size, light in weight, higher in density of discharge ports to be arranged in large numbers, and higher in precision. And, such ink jet heads utilizing heat energy have attached attention in recent years, because they are suitably adapted for color formation, cartridge formation of the so called disposable type, etc.
However, when high speed recording has been practiced by use of a large number of electrothermal transducing elements arranged at high density, the heat energy not utilized directly may be gradually accumulated in some cases. Such heat may have the undesired effect of heating unnecessarily the ink in fine liquid passages, thereby causing viscosity changes to occur, or release of the dissolved gas in the ink to generate unnecessary fine bubbles in some cases.
Accordingly, the present inventors have considered transmitting the heat accumulated in the substrate to the air, the storing portion for the ink (e.g. ink tank), etc. so as to reduce the influence of such unnecessary ink heating given to the discharge performance of ink.
As the constitution of such an ink jet head, for example, as shown in FIG. 5, FIG. 6 and FIG. 7, there has been one in which the heat transmission member 3 to be utilized for transmitting the accumulated heat accumulated in the substrate is adhered to the second ink tank 1 with an ink-resistant adhesive 9, and then the substrate 2 (or so called heater board) having a heat-generating resistance layer to be utilized for discharging of ink formed thereon is adhered similarly with the adhesive 9 to transmit the heat accumulated in the substrate 2 to the second ink tank. For preventing the head of such constitution from ink leak through the adhered surface between the ink tank and the substrate 2 or the heat transmitting member, it is necessary to effect secure adhesion between the second ink tank and the heat transmitting member 3 or the substrate 2, and the adhesive 9 must be filled completely in the gap between the ink tank, heater board 2, the heat transmitting member 3. In addition, for transmitting the heat generated at the heater board 2 with good efficiency, it is necessary that the heater board 2 and the heat transmitting member 3 should be completely adhered to each other. Further, for the purpose of enhancing the shooting precision of the ink discharged from the discharge orifices of the ink jet head, particularly the discharge precision of the ink in shade recording or full-color recording performed by use of a plurality of heads, it is important to control the thickness of the adhesive layer for ensuring the assembling positional precision of the heater board.
However, it has been very difficult to control the amount of the adhesive coated and the coating position for satisfying both the objects of maintaining the positional precision of the heater board 2 relative to the second ink tank after adhesion and preventing ink leakage. In other words, for ensuring the mounting positional precision of the heater board 2, it is preferable that the adhesive 9 should not be preferably coated too thick. In contrast, for the purpose of preventing completely ink leakage, the adhesive should be preferably coated rather thicker. Whereas, if it is coated too thick, there is the fear that superfluous adhesive may be swelled out and flowed into the liquid passages or the ink tank, whereby the production yield of ink jet head may be lowered.